Data communication networks may include various computers, servers, nodes, routers, switches, hubs, proxies, and other devices coupled to and configured to pass data to one another. These devices are referred to herein as “network elements,” and may provide a variety of network resources on a network. Data is communicated through data communication networks by passing protocol data units (such as packets, cells, frames, or segments) between the network elements over communication links on the network. A particular protocol data unit may be handled by multiple network elements and cross multiple communication links as it travels between its source and its destination over the network. Hosts such as computers, telephones, cellular telephones, Personal Digital Assistants, and other types of consumer electronics connect to and transmit/receive data over the communication network and, hence, are users of the communication services offered by the communication network.
Network elements (e.g. Access Points, Mobility Switches and Edge Switches) are typically implemented to have a control plane that controls operation of the network element and a data plane that handles traffic flowing through the network. The data plane typically will have a collection of line cards having ports that connect to links on the network. Data is received at a particular port, switched within the data plane, and output at one or more other ports onto other links on the network. To enable the data to be handled quickly, the data plane is typically implemented in hardware so that all of the decisions as to how to handle the data are performed using hardware lookups, etc. The packets are transferred across the network in accordance with a particular protocol, such as the Internet Protocol (IP).
Ports can fail for many reasons, including line card failure, failure of the link connected to the port (e.g. line cut), far-end line card failure, etc. Likewise, the internal forwarding datapath within the network element may fail which may cause a port or set of ports to appear to have failed, or there may be some other failures along the logical/virtual connection to the port's external peer endpoint. There are numerous reasons why a port may fail.
In the event a port fails, traffic flowing through the port should be diverted to flow out an alternate port to enable connectivity to be restored through the network. To minimize impact on the traffic being handled by the network element, e.g. to minimize downtime and packet loss, the quicker the rerouting of traffic can occur the better. Preferably, it would be advantageous to enable the traffic to fail over to an alternate port in under ten milliseconds (ms). Preferably, the traffic should be spread across the remaining ports rather than all moved from the failing port to a particular designated alternate port to prevent the designated alternate port from being overloaded with traffic.
The current “network overlay” model of integrating Wireless networks with the wired network infrastructure has drawbacks that are alleviated with a newer design called Wireless LAN Split-Plane architecture. In this architecture the basic data forwarding function is pulled out of the Wireless Switches and is incorporated into the existing Routing switches, thus minimizing the monetary cost and network management headaches for Enterprise networks. In such deployments, the Access Point device that performs the Wireless signaling to the Mobile units, is connected via a point-to-point tunnel to one member of a pair of Routing switches that form a Routed Split Multi-Link Trunking (RSMLT) system. RSMLT clusters are used traditionally in networks in order to provide resiliency, redundancy and fast traffic recovery when links are severed or a switch goes out of service.
Over time, the manner in which network elements handle data has evolved. For example, two or more physical links may extend between a group of network elements and be used collectively as a multi-link trunk (MLT). When the links of an MLT are physically connected to two different network elements, the MLT is referred to as a Split Multi-Link Trunk (SMLT). In particular, each of the links in the MLT may be used by either of the network elements to forward data to the other. Thus, if a first network element has data (e.g., a frame/packet) to send to a second network element, the first network element may select one of the links from the MLT and transmit the packet over that link to the second network element.
As noted above, depending on the manner in which the network elements are interconnected, there may be many ways for the network element to forward a frame/packet to enable the frame/packet to reach its destination. As used herein, the term “cluster” is used to refer to one or more nodes providing node-level resiliency at the network level. Logical connections between the cluster nodes are referred to herein as Inter-Switch Trunks (ISTs). ISTs may be physical links that extend from one network element to a neighboring network element in the cluster, or may be logical links that tunnel through one or more intermediate network elements within the cluster. The node that receives a packet will be referred to as a local node. All other nodes within the cluster are referred to as remote nodes with respect to the received packet.
Two or more links may be grouped to form a Multi-Link Trunk (MLT). Each MLT will be assigned a MLT group ID (MLT-ID). An MLT with all its port members only on the local node is referred to as a local MLT group. An MLT group with some of its port members on the local node and the rest on one or more of the remote nodes is referred to as a Split MLT or SMLT group. An SMLT will be assigned a SMLT ID which is a global value within the cluster and unique across the cluster nodes.
When a logical port is implemented as a MLT or SMLT, there are actually multiple physical ports that are capable of forwarding a packet to its next hop on the network. Accordingly, if one of the ports of a MLT/SMLT fails, it would be advantageous to cause the packet to be forwarded on one of the remaining ports so that the packet can traverse the network rather than being dropped. Likewise, rather than designate a primary and backup port for each port in the SMLT, it would be advantageous to load share the packets across the remaining ports of the MLT/SMLT so that the packets may be distributed across the remaining ports that are UP. According to an embodiment, this process is implemented in hardware so that the fastpath (data plane) can automatically accommodate individual and multiple port failures and automatically redirect packet traffic across the remaining ports in an equitable manner.
Wireless Local Area Network (WLAN) split-plane requires data plane or packet forwarding function of the WLAN end devices (mobility units) traffic being handled by the routing switches in the wired network rather than tunneling all the WLAN traffic to centralized controllers. These switches are called mobility switches and they are capable of terminating tunnels initiated by the WLAN access point (AP) devices. They perform the packet forwarding function for the WLAN network.
A significant number of deployments have (routed) split multi-link trunking (SMLT/RSMLT) in the distribution and core layers. (R)SMLT provides redundancy and traffic load balancing of the routing switch nodes. Typical WLAN split plane deployment in a customer network will prefer the mobility switch function be performed by a routing switch in the distribution or core layers. This essentially requires interworking between WLAN split plane and RSMLT.
RSMLT provides resiliency to the network. WLAN split plane is a unique solution to converge the wired and wireless networks. In these converged networks, wired network resiliency capabilities should be extended to the WLAN networks.